1. Field of the Invention
The present invention relates to a carbon nanotube based touch panel, and a display device incorporating the touch panel.
2. Discussion of Related Art
Following the advancement in recent years of various electronic apparatuses, such as mobile phones, car navigation systems and the like, toward high performance and diversification, there has been continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels at the front of their respective display devices (e.g., liquid crystal panels). A user of any such electronic apparatus operates it by pressing or touching the touch panel with a finger, a pen, a stylus, or a like tool while visually observing the display device through the touch panel. Therefore, a demand exists for touch panels that are superior in visibility and reliable in operation.
Up to the present time, different types of touch panels, including resistance, capacitance, infrared, and surface sound-wave types have been developed. Resistance-type touch panels have been widely used, due to their high accuracy and low-cost of production.
A conventional resistance-type touch panel includes an upper substrate, an optically transparent upper conductive layer formed on a lower surface of the upper substrate, a lower substrate, an optically transparent lower conductive layer formed on an upper surface of the lower substrate, and a plurality of dot spacers formed between the optically transparent upper conductive layer and the optically transparent lower conductive layer. The optically transparent upper conductive layer and the optically transparent lower conductive layer are formed of conductive indium tin oxide (ITO).
In operation, an upper surface of the upper substrate is pressed with a finger, a pen, or a like tool, and visual observation of a screen on the liquid crystal display device located on a back side of the touch panel is provided. This pressing causes the upper substrate to be deformed, and the upper conductive layer thus comes in contact with the lower conductive layer at the position where pressing occurs. Voltages are separately applied by an electronic circuit to the optically transparent upper conductive layer and the optically transparent lower conductive layer. Thus, the deformation position can be detected by the electronic circuit.
Each of the optically transparent conductive layers (i.e., ITO layers) is generally formed by means of ion-beam sputtering, and this method is relatively complicated. Furthermore, the ITO layer has generally poor wearability/durability, low chemical endurance, and uneven resistance over an entire area of the touch panel. Additionally, the ITO layer has relatively low transparency. All the above-mentioned problems of the ITO layer make for a touch panel with somewhat low sensitivity, accuracy, and brightness capability.
What is needed, therefore, is a durable touch panel that provides high sensitivity, accuracy, and brightness, and a display device using such touch panel.